Wireless technology opens up more control opportunities
By drawing energy from their environment or from the action of pushing a switch, wireless controllers can dispense with the need for batteries.
By eliminating wiring costs, wireless sensors can increase the scope and flexibility of building-management systems — especially if they do not need batteries. Armin Ander explains.People have sought efficient management of energy-intensive building services such as lighting, heating and air conditioning long before climate-change levies sharpened everyone’s focus on saving wasted energy. Many systems to turn off lights or turn down heating automatically in uninhabited rooms are now available. However, the high costs and inconvenience of rewiring have slowed adoption in commercial or residential properties, but a new generation of wireless technologies may now enable ‘living buildings’ that respond in real time to changes in usage and ambient conditions. Attraction
One of the major attractions of wireless technology is making it possible to install, move and reconfigure equipment quickly and conveniently — and to add new equipment as required. To enhance energy management within buildings, low-cost wireless solutions can eliminate the permanent wiring of large numbers of sensors, monitors and actuators, which enhances flexibility as well as saving time and cost. Offices are frequently reconfigured when companies take on more staff or change operational arrangements. They set-up, remove or reposition partitions, move desks and seating, and even adjust working hours. The moving of equipment as businesses evolve is called churn. Churn imposes high costs on businesses, particularly in terms of lost revenues through disruption to operations and of contractors’ time to implement the changes. Wireless technologies of all types, from building-control infrastructure to office equipment and entry-control systems, provide an effective solution to many of the costs implicit in churn. Low data rate, low-power wireless communications, therefore, should encourage adoption of energy-saving systems. Some examples include single-room controllers to reduce the temperature in rooms that are unoccupied for long periods of time and lower the temperature in corridors, hallways and side rooms to the accepted optimum of 15°C while keeping offices or living rooms warmer at 20 to 22°C. Energy savings
Settings are also adjusted according to the time of day, occupancy and personal settings. Bremer Energieinstitut in Germany has suggested that central single-room temperature controllers could make possible energy savings of 20 to 30%. Similar observations are made in regard to air-conditioning systems. Each degree of increased room temperature reduces the energy requirement for cooling by more than 4% (source: LfU). Window contacts also show enormous energy-saving potential by signalling the heating or air conditioning system to turn off if a window is opened. IFE Krefeld found that the daily energy requirement for heating can be reduced by 40% using window contacts. However, fitting a building with such contacts is normally complex and expensive due to the cabling required. Small radio sensors eliminate these drawbacks, and they can easily be retrofitted. Power
Perhaps the only significant challenge to this vision how each transmitter-receiver will be powered. Battery power is an obvious choice, for ease of installation. However, batteries must be changed at intervals that may range from as long as several years to as little as a few months. In a commercial building with many thousands of nodes, battery replacement presents a significant logistical challenge. Moreover, empty batteries can pose a hazard to equipment as well as a safety risk. Disposal of used batteries also has an environmental impact. Energy harvesting techniques may provide a way forward. These have become well developed in recent times and can harness energy collected from ambient sources such as vibrations, hot surfaces, ambient light or the energy required to push a button. Wireless sensors, such as those provide by EnOcean GmbH can complete a transmission over a practicable range within a total energy budget of about 50 µJ; for reference, pressing the button of a remote control takes several times this quantity. Efficient techniques to collect, store and convert such small quantities of energy now make it possible to send a wireless signal to an HVAC controller using the mechanical energy required to move a window or door handle. The technology has been proven in numerous commercial projects, including the new headquarters complex for SAP in Walldorf, Germany. Two 5-storey buildings totalling 45 000 m2 of floor-space for the entire staff of SAP Germany incorporate 15 000 switches to control lighting and HVAC systems, including external window blinds. EnOcean battery-free wireless switches in ultra-flat switch units save battery-replacement costs and also enable the company to make the most of the flexible partitioning it had specified, even during the planning of the building. Numerous partitions were moved to accommodate team changes while the building was being prepared, and several new offices were created — all without incurring any extra cost or delay through changes to the wiring plan. Experience
Experience is proving that battery-free radio sensors, combining the easy installation and low-churn of wireless connectivity with environmentally-friendly and low-maintenance ambient energy, can finally deliver the decades-old vision of the intelligent, energy-saving building. Armin Ander is vice-president for product marketing with EnOcean GmbH.